1. Field of the Invention
The present invention relates to a printer for printing bit images according to data input from an external data processor such as a host computer.
2. Description of the Related Art
Generally, data fed from an external data processor such a host computer include printing data representing actual printing patterns and control data for controlling a printing method and an operation mode of a print engine of the printer. A controller for the printer processes the printing data by transforming them into dot images or bit ma images to be actually printed out and sends them to the print engine.
The printing data sent from the external data processor are in a form of codes representing characters. Therefore, it is necessary to convert the character codes into bit images of individual characters. In order for that, the printer comprises at least one font memory for transferring the character codes into bit images according to bit image data of a font. The font memory is constituted by a ROM (Read Only Memory) or a RAM (Random Access Memory). When the font memory is constituted by the RAM, all of the bit image data corresponding to at least one font are down-loaded from the external data processor into the RAM.
Generally, in a printer capable of writing images at a high speed, bit image data are stored in a static RAM (which is referred to as the SRAM hereinafter) in which a memory holding operation is not required and an access timing is not limited, therefore, the printer comprising the SRAM is more expensive than a printer comprising a dynamic RAM (which is referred to as the DRAM hereinafter) in which the memory holding operation is required, resulting in that the printer comprising the SRAM in which the bit image data of a variety of fonts are stored becomes extremely expensive.